ES2202278T3 - PROCEDURE AND DEVICE FOR WATER PURIFICATION. - Google Patents

Abstract

Procedure for the purification of residual water in which the residual water (6) to be purified is biologically purified and the discharge (12) is subjected to a dead end membrane filtration (2), in which the retained solid particles they are eliminated by backwashing, characterized in that the biological purification occurs in a stage of filling bodies (1), in which to the discharge (12) of the stage of filling bodies (1) flocculating means (24) are added ) prior to membrane filtration, chemical purification means and / or disinfection means (29) are added during the backwash, the backwash is supported by gas supply (27), especially air, and the liquid Washing (16) that occurs is sent to a pre-clarification (4) connected in front of the stage of filling bodies (1).

Description

Procedure and device for purification of water.

The invention relates to a process for wastewater purification in which the wastewater that is going to be biologically purified and the discharge will be subjected to a dead end membrane filtration in which the particles retained solids will be removed by backwash as well as to the corresponding device.

In countries with low water resources, water Waste represents an important potential as a water source Useful. The replacement of drinking water with purified wastewater allows on the one hand a better use of water reserves existing and on the other hand you can keep the natural sources of water for use in the field of drinking water. For securely reuse wastewater purified, especially municipal wastewater, must however, some requirements of principle are met.

A requirement is the most residual content as low as possible in harmful organic particles. This is achieved according to the current technique in a technically simple way with the help of a solid bed, such as with stages of filling bodies, which due to their simple construction are especially suitable for technically less developed regions of the earth. The second requirement also important, which cannot be satisfied satisfactorily with a solid bed, refers to the quality hygienic wastewater treated, since the wastewater It represents a great source of expansion for diseases infectious

The quality of the discharge of a solid bed can be improved according to the current technique by use of sand filters, but the filtering quality is not yet Enough for reuse. For hygienic reasons you must additionally dosed a large amount of chlorine which can collaborate in the formation of chlorinated organic substances (THN) dangerous.

For the document US-A-5 230 803 a known procedure and a device for purification of wastewater in which water is first purified biologically residual in a solid bed and then subjected to filtration of dead end membrane.

A mission of the present invention now consists of that, avoiding the aforementioned disadvantages, with the use of a solid bed is purified in such a way the residual water that the purified wastewater quality allows reuse as useful water, especially for irrigation purposes.

The procedure according to the invention stands out by the features of claim 1. The corresponding device is characterized by the characteristics of the claim 4.

In dead end membrane filtration both microfiltration membranes can be used as well as ultrafiltration membranes. Due to this way of operation and after the membranes retain the solid particles, they produces an increase in the concentration of solid particles in the membrane module or in the modules membrane of the membrane filtration system. These solid particles are extracted, preferably in shape periodic, of the membrane surface by means of devices planned and removed from the system.

The invention can be used independently of the type of membrane module used (tubular, plate module, hollow fiber as well as mattresses).

Other advantageous device configurations according to the invention are expressed in the claims Dependents

A membrane filtration according to a treatment Biological wastewater offers the following advantages:

- the membranes represent an absolute barrier corresponding to the diameter of the pores,

- organic solid particles in suspension they are totally separated and the discharge is free of particles,

- pathogenic germs are eliminated with all security and also the number of virus particles,

- the installation download complies without limitation, with regard to hygienic quality, the WHO requirements for irrigation purposes.

In addition the filtration according to the principle of dead end has the advantage that energy consumption is lower compared to a membrane filtration in service of cross flow and a membrane filtration facility of dead end has less space occupation than the rafts of clarification and the sand filter that are usually placed after a solid bed, especially a stage of bodies of filling.

Additionally, when using washes to periodic countercurrent wastewater can be used purified (filtered) thereby reducing the consumption of drinking water.

To better purify the module the wash to Counter current is supported by gas injection, especially air. A vertical arrangement of the modules causes a distribution and a balanced and more effective mixing of the washing air and the liquid.

The washing liquid heavily loaded with solid particles are sent at least partially to a preclarification connected before the solid bed reactor.

Alternatively or for a partial current of washing liquid may be provided that the washing liquid that is produced in backwash be removed as a mud surplus. In this way you can download the preclarification of the solid bed

For this, because of the discharge of the solid bed flocculant media are added, the particles are achieved solids gather in larger flocs and with it the residual water It can be filtered more easily and the installation modules Membrane filtration are better washed against the current.

The purification of the membranes is carried out during backwashing by dosing means of purification and / or means of disinfection saving time and improving the costs.

If the solid bed discharge is sent to a separation of solid particles from a postclarification stage and then to the dead end membrane filtration, increase the filtration capacity because of the lower solid particle concentration of wastewater as well as lengthen the intervals of backwash and purification. Therefore an existing postclarification stage can be interspersed in the process according to the invention.

The invention will be clarified by way of example about The base of the figure. The figure shows the integration of a membrane filtration installation, now called hereinafter abbreviated filtration installation, in a treatment plant.

With filtration installation 2 the Biologically purified residual water. In this installation treatment plant the raw waste water 6 crosses a measurement section 30, a sand catchment 31 as well as a preclarification raft 4 with sludge separation 7 built as EMSCHER wells. Water waste 8 previously decanted is sent to the reactor of bodies of filling 1 with the filter load 11. The discharge 12 of the reactor filling bodies 1 is taken in constant quantities from a well (not shown) directly after the reactor of bodies of fill 1 and / or directly along a line 36 from a raft of postclarification 22 using a submerged pump 26. Discharge 12 reaches flocculation raft 23 in which a medium is dosed flocculant from a flocculant medium tank 25 by means of a Dosing pump 34. From this flocculation raft 23, feeds the filtration system 2 by means of a pump circulation 13.

Feed pipe 35 can be blocked during backwash using the lock key twenty.

At the upper end of the filtration module 14 is a two-way valve 19 (valve for water washed). During filtration the valve for the wash water 19 is closed, with what is formed the so-called "end dead. "After the membrane filtration module 14 retain solid particles, an additional step of filtration with the solid particles gathered like a mud. The filtered 15 passes radially through the membrane and flows to through the filter valve 18 in the filter vessel 3. The filtrate 15 flows through a flowmeter not represented and collected in a filter container 3. The Filtering can be removed by filtering discharge 21.

During backwash it is pumped filtered in the opposite direction in the filtration module 14 by means of a wash pump 17 that is in the container filtered 3, built for example as a submerged pump. One valve 3-way (filter valve 18) switches between both streams. The wash water valve 19 is open during washing a countercurrent to separate the wash water 16. The amount of wash water 16 can be calculated with the flow meter 32

A better effect of purification, before backwashing, by means of discharge of the liquid from the filtration module 14 by washing countercurrent below. During the download the tap lock 20 is closed as well as open the water valve of wash 19 and lock tap 37.

The necessary recirculation flow of 0.5 - 1 in the filler body reactor 1 to ensure separation Hydraulic biomass can be obtained by returning water wash 16 to the preclarification pool 4.

The initial module lock issues, which were caused by the high percentage of solid particles of the residual water could be solved with the modification of the washing to countercurrent

Modified backwashing stands out for a combined wash with water and air. In it, on the side of power is injected a large amount of air into the module before of backwash as well as during washing countercurrent With this the solid particle cake disintegrates And it can be easily transported. To do this before entry to the module is an inlet for washing air 27. A through it it can be blown further into the wash module to countercurrent air through compressor 28 that supports the power supply With the right membranes you can provide air also from the filtrate side.

The filtration module 14 can be horizontal for better distribution of washing air 28, however It can also be located vertically. In the layout recently mentioned, with modified backwash according to the following mode, no blockages were detected even with a high content of solid particles:

- 20-30 min. production time (filters)

- 20 s prewash with power

- 20 s backwash of the filtrate

- 20s backwashing of the filtrate and prewash with feed + air mixture

Another improvement of backwashing the originates the simultaneous use of chemical products. With it can greatly reduce fouling inorganic, organic and biological membrane.

Depending on the type and intensity of fouling, they can use different chemicals in different concentrations. In the installation according to the figure you have proven to be an effective backwash with acid and then a hypochlorite wash.

In chemical backwashing, dose a chemical purification medium and / or a medium of disinfection 29 in the backwash stream by a membrane pump 33. The duration as well as the interval of Chemical backwashing are adjustable and depend on the degree of fouling of wastewater and ambient temperature.

The installation described by way of example It also has the following characteristics: filling body reactor 1 contains 80 -100 mg.l -1 of non-filterable particles and has a CSB of 100-150 mg.l -1. The unloading of the raft of postclarification 22 presents 10-60 mg.l -1 of non-filterable particles and a CSB of 55-90 mg.l -1. Time Flocculation is 15-20 min. Dosing pump 34 for the flocculating medium uses a compression pump by hose.

The filtration system 2 consists of a filter module 14 for a total membrane area of 5.1 m2. The membrane material is PVDF (fluoride polyvinylidene).

Due to previous knowledge from trials in laboratory, during production the filtering current The resistance of the membrane, which goes increasing, is compensated by the increase in pressure of feeding. The average feed pressure is therefore preferably 0.3 to 0.6 bar, however maximum 0.8 bar.

Claims (7)

1. Procedure for the purification of residual water in which the residual water (6) to be purified is biologically purified and the discharge (12) is subjected to a dead end membrane filtration (2), in which the particles retained solids are removed by backwash, characterized in that biological purification occurs in one stage of filling bodies (1), in which to the discharge (12) of the stage of filling bodies (1) flocculating means (24) are added before membrane filtration, during backwashing are added chemical purification means and / or disinfection means (29), backwash is supported by input of gas (27), especially air, and the washing liquid (16) that is produces is sent to a preclarification (4) connected in front of the stage of filling bodies (1). 2. Method according to claim 1, characterized in that backwashing is carried out with filtration (15) of the dead end membrane filtration (2). Method according to one of claims 1 or 2, characterized in that the washing liquid (16) produced in the backwash is extracted as excess sludge. 4. Device for the purification of waste water comprising a fixed bed reactor (1) for biological purification, in which after the fixed bed reactor (1), on the discharge side, a filtration installation is provided by dead end membrane (2) for purification of the discharge (12) of the fixed bed reactor (1), characterized in that the fixed bed reactor (1) is constructed as a reactor of filling bodies, to separate the washing liquid (16) the dead end membrane filtration system (2) is attached with a pre-clarification raft (4) of the body reactor filling (1), on the discharge side after the reactor of filler bodies (1) a device (25, 34) is provided for the adding flocculant media (24) to the discharge (12), a device (17, 18) is provided for the backwashing of retained solid particles, the which presents a device (33) for the addition of a product chemical purification and / or a means of disinfection (29), to support backwashing is provided a device (28) for gas injection, especially air (27), at the end membrane filtration system dead (2). 5. Device according to claim 4, characterized in that the dead end membrane filtration system (2) has micro or ultrafiltration membranes. Device according to one of claims 4 or 5, characterized in that a filtering vessel (3) is provided to collect the filtrate (15) from the dead end membrane filtration system (2), which is connected to the device (17, 18) for backwashing. 7. Device according to one of claims 4 to 6, characterized in that the dead end membrane filtration installation (2) has filter modules (14) positioned vertically.